Fertility – Basic Facts (5)

ABOUT FERTILITY – is the man always fertile, is the woman always fertile ?

The fertility of the couple is a shared fertility.The man is always fertile from puberty onwards for the rest of his life, (1) the woman is fertile for just some days in the menstrual cycle, this means the woman’s fertility is cyclical.

What is the sperm, what is the ovum ?

The reproductive cell is known as the gamete. The male gamete is the sperm, and is produced by the male gonad, the testis. The female gamete is the ovum (egg) and is produced by the female gonad, the ovary. The gamete differs from other cells in the body as its nucleus contains just 23 chromosomes, while all other cell nuclei contain 46 chromosomes. The chromosomes carry DNA, the genetic material unique to each individual. Fertilization is when the nucleus of the sperm and the nucleus of the ovum fuse together, (2) and is the beginning of a new human individual who has a full DNA complement of 46 chromosomes unique to him/her alone, having received half the genetic material from the mother and half from the father.

A major difference between the male sperm and the female ovum is that in the male, sperm continue to multiply in adult life while the female will make no new ova after birth. (3) This means that every girl when she is born already has the finite number of oocytes (called primordial follicles) to last her child-bearing years.

During each menstrual cycle a small number of these primordial follicles start to mature under stimulation by follicle stimulating hormone (FSH) from the pituitary gland, and one follicle (sometimes two follicles) continues to grow and becomes dominant. (Link to 6a menstrual cycle). The dominant mature follicle is called the Graafian follicle and consists of the ovum surrounded by follicular fluid. During the follicular phase the oocyte increases in size from 15micron to 135micron* when mature, to become one of the largest cells in the body as it has to sustain the pregnancy until implantation occurs.5 (* 1 micron = 0.001mm = one thousandth of a millimetre).

OVULATION, FERTILIZATION, IMPLANTATION:

When the Graafian follicle has reached its maximum size, (about 2.3cms due to the increase in follicular fluid), it ruptures, releasing the mature ovum into the outer end of the fallopian tube; (LINK for diagram to 6c, Fig. 6-9). This event is called ovulation and is triggered by the luteinizing hormone (LH surge) from the pituitary gland. The ovum lives for 24 hours after it is released and it is fertilizable for only 12 – 16 hours during those 24 hours. Fertilization takes place in the outer end of the fallopian tube. (LINK for diagram to 6e, Fig. 6-16) The fertilized ovum travels down the fallopian tube to the uterus and implantation occurs seven days later in the endometrial lining of the uterus.4 (LINK for diagram to 6e, Fig.6-17).

The child-bearing years last about 35-40 years and the last menstrual cycle occurs when the quota of ova have been exhausted. This marks the arrival of the menopause. (LINK to 17, Menopause)

  1. Odeblad Erik; ‘The discovery of different types of cervical mucus and the Billings Ovulation Method’; Bulletin of the Ovulation Method Research and Reference Centre of Australia, Vol 21, No3; 3-35; Sept 1994. (on the internet if you google ‘Erik Odeblad, cervical mucus’)
  2. Flynn, Anna & Brooks Melissa; ‘The Manual of Natural Family Planning’ p32; 1996; ISBN 0 7225 3115 X
  3. Lamb JF, Ingram CG, Johnson IA, Pitman RM; ‘Essentials of Physiology’ 3rd Edition, page 252;Blackwell Scientific Publications 1991, ISBN-632-03135-2
  4. Griffin JE, Ojeda SR; ‘Textbook of Endocrine Physiology 3rd Edition,1996, page 226; Oxford University Press, ISBN 0-19-510755-1 (pbk)
  5. Manassiev Nikolai, Whitehead, Malcolm; ‘Female Reproductive Health’; p7; 2004; ISBN 1-85070-491-0

To be most effective, the woman must be taught the Symptothermal Double-Check Method of Natural Family Planning by a qualified natural family planning teacher.